1. Field of the Invention
The present invention relates to a transmission for use in cars, agricultural machines, construction machines, industrial machines, and the like. More particularly, the invention relates to a ratchet one-way clutch using a ratchet (a pawl member) as a lock mechanism, which is a type of one-way clutches with functions of backstop and the like, and can be used in automatic transmissions of vehicles, and the like, and a stator apparatus using such a ratchet one-way clutch.
2. Related Background Art
A one-way clutch for use in automatic transmissions generally includes an inner race, an outer race relatively rotatable to the inner race, and a sprag or roller for transmitting torque between the inner and outer races. Upon engagement of the sprag or roller with a raceway surface of the inner race or outer race, or a cam surface formed on the raceway surface, rotating torque is transmitted in one direction only. Idling between the outer and inner races occurs in the opposite direction.
Among those one-way clutches, there is a ratchet one-way clutch using a ratchet as a torque transmitting member for transmitting torque between outer and inner races. The ratchet one-way clutch includes an outer race having a pocket on its inner periphery, an inner race disposed coaxially with the outer race and having a notch on its outer periphery, a pawl member contained in the pocket, and, when meshed with the notch of the inner race, bringing the one-way clutch into a locked condition to transmit torque between the outer and inner races, and an elastic member, such as a spring, for biasing the pawl member toward the inner race.
In the above-discussed ratchet one-way clutch, when the clutch is under the condition of rotation in one direction, the pawl member freely slides on the outer periphery of the inner race to cause a relative idling between the inner and outer races. Upon rotation of the one-way clutch in the opposite direction, the pawl member meshes with the notch to bring the clutch into a lock-up condition.
FIGS. 12 and 13 illustrate a conventional ratchet one-way clutch used in a stator of a torque converter 91. FIG. 12 is a front-side cross-sectional view of the ratchet one-way clutch, and FIG. 13 is an axial cross-sectional view of FIG. 12.
The torque converter 91 includes an stator impeller 94 having an outer race portion 93 on its inner periphery, an inner race 92 having recesses 104 on its outer periphery and disposed coaxially with the outer race portion 93, a pawl member 100 contained in a pocket 105 formed on the inner periphery of the outer race portion 93 to transmit torque upon engagement with the recess 104, a basing member 101 disposed in an indent 106 formed in the pocket 105 to bias the pawl member 100 in a radially-inward direction, a bush 96 slidably arranged on the inner race 92 to support the pawl member 100 and the biasing member 101 along an axial direction, and a snap-ring 97 for preventing the bush 96 from slipping off. A wave spring is mainly used as the biasing member 101.
When the ratchet one-way clutch is used in the stator as in the above-discussed conventional structure, abnormal noises are likely to occur due to the backlash at the time of engagement between the pawl member and the recess. A damper structure is accordingly considered to prevent the occurrence of abnormal noises.
FIGS. 10 and 11 illustrate another conventional ratchet one-way clutch disclosed in Japanese Patent Application Laid-Open No. 2002-13559. FIG. 10 is a front-side cross-sectional view of this conventional clutch used in a stator 60, and FIG. 11 is a cross-sectional view taken along a line 11—11 in FIG. 10.
As illustrated in FIG. 10, the stator 60 includes an inner race 62 having recesses 81 on its outer periphery, an outer race member 63 provided coaxially with the inner race 62 and having pockets 72 and indents 73 on its inner periphery, a pawl member 70 contained in the pocket 72 such that torque can be transmitted between the inner race 62 and the outer race member 63 when engaged with the recess 81, a biasing member 71 arranged in the indent 73 to aid the pawl member 70 to mesh with the recess 81, an operating member 68 rotatable relative to the outer race member 63, a spring 65 disposed in a space 74 formed between the outer race member 63 and the operating member 68, and sheet members 69 placed at opposite ends of the spring 65.
A pair of portions 77 protruding in a radially-outward direction are formed on diametrically-opposite portions of the outer periphery of the outer race member 63, respectively. Further, a pair of portions 78 protruding in a radially-inward direction are formed on diametrically-opposite portions of the inner periphery of the operating member 68 disposed outside the outer race member 63, respectively. End faces 75 and 76 of the protruding portions 77 and 78 are opposed to each other with a predetermined clearance therebetween.
In addition, a pair of protruding portions 79 with a circumferential length shorter than that of the protruding portion 77 are diametrically formed between the protruding portions 77 of the outer race member 63. A pair of protruding portions 80 with a circumferential length shorter than that of the protruding portion 78 are diametrically formed between the protruding portions 78 of the operating member 68. The above space 74 is a circumferential clearance between end faces of the protruding portions 79 and 80, in which the spring 65 is sandwiched between the sheet members 69.
As illustrated in FIG. 11, the outer race member 63 has an annular extension portion 66 extending in a radially-inward direction. The extension portion 66 supports the pawl member 70 and the biasing member 71, and acts as a bush sliding on outer periphery and side of the inner race 62. In the stator 60, side surfaces 85 and 86 of a radially-inner portion 84 in the operating member 68 and the outer race member 63 act as a receiving surface for a needle bearing (not shown). A snap-ring 67 prevents the outer race member 63 from slipping off. A reference numeral 64 denotes a stator impeller.
In the ratchet one-way clutch as illustrated in FIGS. 12 and 13, however, recesses for engaging with the pawl member are arranged with a predetermined pitch along a circumferential direction of the race. Accordingly, when the rotational direction changes from an idling direction to a meshing direction, the backward movement of the pawl member within an amount of the predetermined pitch occurs before the pawl member meshes with the recess.
The above-discussed engagement between the pawl member and the recess inevitably accompanies shock and noises due to the shock. Accordingly, it is considered that the outer race and the stator impeller are assembled in a relatively-rotatable manner and a damper spring for forming the damper mechanism is interposed between the outer race and the stator impeller, such that the shock can be alleviated and the occurrence of noises can be prevented.
A fluid oil pressure, however, appears when the stator impeller rotates in a torque converter, and the outer race and the stator impeller are likely to be pressed against each other in an axial direction. Thus, the relative rotation between the outer race and the impeller required by the damper mechanism is inhibited or weakened, resulting in undesired wear and occurrence of much wear powder. Where the outer race and the stator impeller are made of aluminum, which is adopted in an embodiment of the present invention described later, the above problem is more likely to arise since a sliding contact is effected between the same material of aluminum.
Further, when it is considered that stress is dispersed to maintain the strength of the outer race, it is preferable to replace angled corner portions in the contour of the pocket by arcuate portions as much as possible. On the other hand, the biasing spring disposed in the pocket is formed of steel, and the hardness of the spring is hence greater than that of the outer race. Therefore, the biasing spring rattles in the pocket due to incessant up-and-down movements of the pawl member at the time of idling and vibrations transmitted from the driving shaft and the like, resulting in wear of the outer race where the spring is in contact with the outer race. In particular, when the biasing spring is an accordion-type spring, an angled portion of the spring is brought into a linear contact with an arcuate inner wall of the pocket. Accordingly, the condition of the spring in the pocket becomes more unstable, and the wear resultantly increases.
Furthermore, the stator undergoes a fluid pressure in the torque converter, and the outer race member is hence pressed against the stator wheel (stator impeller). Therefore, when the damper mechanism operates, the outer race member and the stator wheel are subjected to the wear to impair a smooth relative rotation, similar to the conventional apparatus of FIGS. 12 and 13. This situation goes worse because of fusion or melting of material when both of the outer race member and the stator wheel are formed of aluminum.
It is an object of the present invention to achieve a smooth relative rotation between two members of a damper mechanism, suppress wear due to a sliding motion and occurrence of wear powder due to the wear, stabilize the operation of a spring used as a biasing member, and suppress wear due to a rattling movement of the spring and occurrence of wear powder due to the wear.
It is another object of the present invention to achieve a smooth operation of a damper mechanism in a stator.
It is another object of the present invention to provide a ratchet one-way clutch which includes an inner race, an outer race provided coaxially with the inner race, a pawl member for transmitting torque between the inner race and the outer race, and a damper mechanism for absorbing shock at the time of engagement of the pawl member, and in which a sliding plate is interposed between two members that constitute the damper mechanism and are rotatable relatively to each other.
It is another object of the present invention to provide a ratchet one-way clutch which includes an inner race, an outer race provided coaxially with the inner race, a torque transmitting member disposed in either of the inner race and the outer race, and a biasing member for biasing the torque transmitting member, and in which a protecting member is interposed between the biasing member and one of the inner race and the outer race wherein the torque transmitting member is provided.
It is still another object of the present invention to provide a stator apparatus which includes an outer race member of a one-way clutch assembly, a stator wheel rotatable relative to the outer race member, and a damper mechanism, and in which an extension portion extending in an axial direction is formed in one of the outer race member and the stator wheel, a window corresponding to the extension portion is formed in the other of the outer race member and the stator wheel, the extension portion extends through the window to provide a protruding portion on the side of a side surface of the other of the outer race member and the stator wheel, and the protruding portion of the extension portion is supported by a bearing.